1. Field of the Invention
This invention relates generally to water permeable fiber systems and the preparation of the fibers, and more particularly to a system employing such fibers for plant irrigation where the fibers serve as an osmotic valve to dispense water upon demand by the plants.
2. Description of Related Art
An important aspect of the cultivation of plants is providing the proper amount of water. Not only do different types of plants require different amounts of water, but the humidity of the environment has an effect on the quantity of water which must be supplied. As a result, a substantial amount of time is expended to determine whether additional water is needed by a plant as well as actually providing it. Shopping malls, botanical gardens, plant nurseries and other places having a large number of plants therefore require employees solely for the care of the plants. Even where employees are provided solely to care for plants, the possibility of over or under watering of plants remains.
U.S. Pat. No. 4,527,354, Sellier, entitled: "Implantable Reservoir for automatic Watering of Plants", discloses a reservoir which is placed in the bottom of a pot and has wicks extending from the reservoir into the soil in which the plant is growing. A tube with a float gauge is included so that the water may be replenished.
The preparation of hollow cellulose acetate fibers by either hot melt extrusion or a melt spin process, results in a fiber wall having an asymmetric permeability. These hollow fibers have been used in a reverse osmosis system which applies a pressure higher than osmotic pressure to a mixture such as saline water, to cause pure water from the mixture to pass through the fiber wall into the tube. McClain et al. in U.S. Pat. No. 3,423,491 describe the preparation of such fibers.
U.S. Pat. No. 3,873,653, Meinecke et al, entitled: "Preparation of High Flux Cellulose Acetate Membranes and Hollow Fibers from Prefabricated Low Flux Specimens", discloses a process for improving the fibers disclosed by McLain so as to increase the rate at which pure water can be produced by desalinization using the fibers in reverse osmosis. It is noted that the amount of water extracted by these fibers decreases with the passage of time, requiring further treatment every 180 hours or so to maintain its improved efficiency.
The need for treatment or osmotic regeneration results from particles clogging the pores, and is a problem with prior art systems.